In general, a disk drive, e.g., a magnetic disk drive, comprises a magnetic disk in a case, spindle motor configured to support and rotate the disk, head stack assembly that supports magnetic heads, circuit board unit, etc. The head stack assembly comprises a bearing and head gimbal assemblies extending from the bearing. Each head gimbal assembly comprises a suspension supporting the magnetic heads and a conductor trace that electrically connects the heads to the circuit board unit.
The circuit board unit integrally comprises a base portion, on which a head IC, connectors, etc., are mounted, and a main flexible printed circuit board (main FPC) extending from the base portion to the vicinity of the bearing. An extended end portion of the main FPC constitutes a plurality of terminal areas, each of which carries a plurality of connection pads thereon. The terminal areas are attached to the bearing of the head actuator.
The conductor trace on the suspension has one end connected to the magnetic head and the other end constituting the terminal areas. The terminal areas each comprise a plurality of connection terminals connected individually to conductors. These connection terminals are soldered to their corresponding connection pads of the main FPC. The magnetic head is electrically connected to a circuit board unit through the conductor trace and main FPC.
In order to further increase or improve the capacity and reliability of modern disk drives, addition of various functions is being discussed. The additional functions include an HDI sensor, a two-step actuator, a reading function, a DFH function, high-frequency- or heat-assisted recording, etc. In adding these functions, it is necessary to increase the number of connection terminals at a terminal area on the rear end side, as well as the number of conductors of the conductor trace. However, the size of the rear-end-side terminal area is limited. In the case of an extended design based on the conventional soldering system, therefore, the possibility of a short-circuit due to solder bridging increases if nine or more terminals are arranged on the terminal area. Thus, it is urgent to establish an effective connection system to cope with a further increase in the number of terminals in each set.